Source : Webster's Revised Unabridged Dictionary (1913)

Oppositive \Op*pos`i*tive\, a. [Cf. F. oppositif. See
   {Opposite}.]
   Capable of being put in opposition. --Bp. Hall.

Source : WordNet®

oppositive
     adj : expressing antithesis or opposition; "the adversative
           conjunction `but' in `poor but happy'" [syn: {adversative}]